JP4804814B2 - Press-fit terminal - Google Patents

Description

  The present invention relates to a press-fit terminal having a connecting portion that is inserted into a conductive through-hole of a substrate incorporated in an electronic device in a press-fit state and electrically connected through the through-hole. The present invention relates to a press-fit terminal that is optimally used in a control device used in a severe environment such as high temperature and high humidity.

  Conventionally, as a method of fixing a terminal such as a printed circuit board and a terminal, a terminal called a press-fit terminal is inserted into a conductive through hole provided on the board, and the terminal is mechanically fixed without soldering. The method is known.

  The press-fit terminal is arranged between the guide part inserted into the through hole of the board, the mounting part to be mounted on the board connector, etc., and between the guide part and the mounting part, and has a width larger than the through hole diameter. And a connecting portion that is inserted in a press-fitted state inside the through hole.

  The press-fit terminal is inserted into the through hole of the board from the guide part, and the contact load is generated by press-fitting the connecting part with a width larger than the through hole diameter into the through hole, increasing the mechanical holding force. Stable electrical connection can be obtained.

The substrate is generally formed by a combination of glass fibers in a matrix laminated number of sheets impregnated with epoxy resin bonding, a wiring circuit pattern by the conductive member on the surface, and a through hole penetrating the front and back of the substrate Is provided. The through hole of the substrate is plated with copper plating or the like from the wall of the inner peripheral surface of the through hole to the periphery of the through hole opening on the surface of the substrate. It is electrically connected to the circuit pattern.

  When a press-fit terminal is press-fitted into the through hole of the board, the press-fit connection part of the press-fit terminal first contacts the opening edge of the through hole and a load is applied, and the press-fit connection part is elastically plastically deformed into the through hole. Press fit.

  In order to obtain electrical connection reliability, a substrate used in a control device having a large vibration such as an automobile needs to secure a sufficient fixing force to the substrate of the press-fit terminal. Therefore, in order to obtain a high holding force, for example, a press-fit terminal of a high load type in which the width of the press-fit connection portion is formed larger than the diameter of the through hole and the press-fitting white is increased is known (for example, Patent Document 1).

JP 2004-127610 A

  By the way, when a high-load type press-fit terminal is press-fitted into a through-hole of the substrate, the plating at the periphery of the through-hole opening of the substrate is damaged due to stress concentration at the time of press-fitting the press-fit terminal, and the plating is likely to be broken.

  Further, in this case, when the stress around the through-hole opening of the substrate acts in the surface direction of the substrate, each impregnated sheet of the laminate constituting the substrate is peeled off, which may damage the substrate itself.

  Especially when the board is used in a harsh operating environment where the ambient temperature is high, humid, and vibration is applied, such as in a control device of an automobile, the board itself when press-fitting a press-fit terminal is used. There is a concern that the damage given may greatly deteriorate the substrate characteristics such as insulation.

  Therefore, when press-fitting a high-load type press-fit terminal, apply a lubricant called contact oil on the surface of the press-fit terminal to reduce the press-fitting load and press-fit the press-fit terminal into the through hole. Wearing was done.

  However, there is a problem that applying the contact oil at the time of the work of installing the press-fit terminal is very troublesome for the oil application work. In addition, the material cost of the contact oil is required, and there is a problem that the work of attaching the press-fit terminal becomes expensive in combination with a decrease in workability.

  The problem to be solved by the present invention is to provide a press-fit terminal in which through-hole plating does not occur even when contact oil is not applied to the terminal when press-fitting the press-fit terminal into the through-hole of the substrate. It is in.

The present invention relates to a through-hole in a press-fit terminal that is inserted in a press-fit state without applying contact oil into a through-hole of a circuit board formed by laminating and pressing a sheet of glass fiber impregnated with an epoxy resin. The gist of the press-fit terminal is that the maximum value of the pressure Pd applied to the through hole represented by the following formula (1) when inserted is 500 MPa or less.
Pd = Fd / S (1)
In the above equation (1), Fd is the total force applied from the press-fit terminal to the through hole, and is expressed by the following equation (2), and S is the contact area between the press-fit terminal and the through hole.

上記（２）式において、μはプレスフィット端子とスルーホールの摩擦係数であり、Ｐｉは接触荷重であり、θはプレスフィット端子とスルーホールの接触角である。

In the above equation (2), μ is the friction coefficient between the press-fit terminal and the through hole, Pi is the contact load, and θ is the contact angle between the press-fit terminal and the through hole.

  According to the press-fit terminal according to the present invention, since the maximum value of the pressure Pd applied to the through hole is formed to 500 MPa or less, even when the holding force of the press-fit terminal is increased to obtain a high load type terminal. When the press-fit connection part is press-fitted into the through hole of the substrate, it is possible to prevent the through hole from being plated out. Furthermore, there is no fear of damaging the substrate itself during press-fit terminal press-fitting, and the substrate characteristics are not deteriorated.

  Since the present invention can press-fit even a high-load type press-fit terminal without using contact oil, it eliminates the need to apply contact oil and improves the workability of terminal crimping. Costs in work can be reduced.

  Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. First, the results of studying the mechanism by which plating of through-holes in a substrate occurs will be described. FIG. 1 is an explanatory diagram showing the force applied when a press-fit terminal is inserted into a through hole of a substrate. In FIG. 1, 1 is a press-fit terminal, 2 is a substrate, and 3 is a through hole.

  Although not shown in FIG. 1, the substrate 2 has various conductive paths formed on the surface thereof, and a large number of through holes 3 are opened. Plating is formed on the inner peripheral surface and the opening peripheral edge of the through hole 3 by copper plating or the like and connected to the conductive path on the surface of the substrate 2. In FIG. 1, the shape of the press-fit terminal 1 is an approximate shape.

  As shown in FIG. 1, when the press-fit terminal 1 is inserted into the through hole 3 of the substrate 2, when a certain amount of the press-fit terminal 1 is inserted, the peripheral edge of the through hole 3 is contacted. From this point, a load is applied to the press-fit terminal 1 and the through-hole periphery 3 a of the substrate 2, and the press-fit terminal 1 is press-fitted into the through-hole 3.

  At this time, the force applied to the peripheral edge 3 a of the through hole is a resultant force Fd of the frictional force μN from the connecting portion of the press-fit terminal 1 and the vertical drag N. It is considered that the through hole 3 is deformed by this force Fd and the plating of the through hole 3 is broken. On the other hand, when contact oil is applied to the press-fit terminals, the frictional coefficient μ is reduced, and the frictional force μN is reduced. It seems that it can be prevented.

  As shown in FIG. 1, when the force applied to the inner wall 3b of the through hole is disassembled when viewed from the through hole 3 side, Pi is a contact load (contact direction reaction force), μ is a friction coefficient, N is a vertical drag, and θ is a contact. Corners and Fi are insertion forces. Here, the total sum of the forces applied to the through holes is Fd. This total force Fd is expressed by the following equation (2).

When the contact area (only one side) between the terminal and the through hole at each moment of insertion is S, the pressure Pd applied to the plating in the through hole is expressed by the following equation (1).
Pd = Fd / S (1)

  Focusing on Pd in equation (1), the relationship between this numerical value and through-hole plating breakage was examined for high-load type press-fit terminals. It was clarified that the through hole was not cut below this value. This value was 500 MPa.

The pressure Pd applied to the plating can be obtained by the following means. The following formulas (3) and (4) are derived from the relationship of force balance shown in FIG.
N · sin θ = Pi + μN · cos θ (3)
Fi = Ncos θ + μN · sin θ (4)
In FIG. 1, the resultant force of the component force N and the component force μN is Fd, and Fd is expressed as the following equation (5).

  The vertical drag N is expressed by the following equation (6) from the above equation (3).

  If the contact load Pi, the contact angle θ, and the friction coefficient μ are known from the above equation (6), the normal drag N can be obtained. Then, Fd can be calculated using the vertical drag N from the above equation (2). Further, when the contact area S is obtained, the pressure Pd applied to the plating of the through hole is obtained by dividing Fd by the contact area S from the equation (1).

  An example in which the Pd value is actually obtained for the needle eye type press-fit terminal shown in FIG. As shown in FIG. 2A, the needle eye type press-fit terminal is tapered at one end of the press-fit terminal 1 as a guide portion 11 that guides a terminal inserted into the through hole 3. The other end side is formed as a mounting portion 12 to be attached to a board connector housing or the like (not shown) by press-fitting or the like, and an intermediate portion is formed as a connection portion 13 in contact with the through hole.

  The press-fit terminal 1 in FIG. 2A is provided with a slit portion 14 penetrating the elongated terminal 1 in the axial direction at a central connection portion 13. FIG. 2B is a cross-sectional view taken along line AA of the connection portion 13 in FIG. As shown in FIG. 2B, the two beam members 15 and 16 having a substantially square cross section are arranged so as to face each other across the slit portion 14, and the beam members 15 and 16 are bent in the direction of the slit portion 14. Therefore, it is formed to be capable of elastic-plastic deformation. The needle eye type press-fit terminal 1 reduces the insertion force when the connecting portion 13 is press-fitted into the through-hole 3 by elastically deforming the beam members 15 and 16 of the connecting portion 13 and after insertion. A high holding force with respect to the through hole 3 is obtained by the elastic force of spreading in the direction opposite to the slit portion 14 of the beam members 15 and 16.

  A press-fit terminal 1 shown in FIG. 2A is formed by pressing a metal wire having excellent conductivity such as a copper alloy. Although not particularly illustrated, the surface of the connecting portion 13 that comes into contact with the through hole of the press-fit terminal 1 is plated with tin or the like.

  A press-fit terminal having the shape shown in FIG. 2A was inserted into the through hole, and the insertion force, contact load, contact angle, contact area, and the like with respect to the insertion amount were measured. 3 to 7 are graphs showing the relationship between the amount of press-fit terminal insertion and each value. In this case, the press-fit terminal was inserted without applying contact oil.

  FIG. 3 is a graph showing the relationship between the insertion amount and the insertion force Fi, where the horizontal axis represents the insertion amount (mm) and the vertical axis represents the insertion force Fi (N). The amount of insertion was set to 0 mm when the connecting portion 13 of the press-fit terminal 1 was in contact with the periphery of the opening of the through hole 3. As shown in FIG. 3, the insertion force gradually increases as the press-fit terminal 1 is inserted into the through hole 3. When the insertion amount is constant, the insertion force becomes the maximum value, and then decreases and becomes constant. Even if the insertion amount is increased, the constant insertion force is maintained.

  FIG. 4 is a graph showing the relationship between the insertion amount and the contact load Pi, where the horizontal axis is the insertion amount (mm), and the vertical axis is the contact load Pi (N). As shown in FIG. 4, the contact load Pi increases as the press-fit terminal is inserted, and the contact load Pi becomes maximum at the insertion amount where the insertion force becomes maximum. Pi is maintained.

  FIG. 5 is a graph showing the relationship between the insertion amount and the contact angle θ, where the horizontal axis is the insertion amount (mm) and the vertical axis is the contact angle θ (deg). The contact angle θ depends on the shape on the insertion side of the press-fit terminal. In the case of the press-fit terminal having the shape shown in FIG. 2A, the contact angle θ changes as shown in FIG.

FIG. 6 is a graph showing the relationship between the insertion amount and the contact area S, where the horizontal axis is the insertion amount (mm), and the vertical axis is the contact area S (mm ² ). The contact area S of the press-fit terminal having the shape shown in FIG. 2A changes as shown in FIG. The contact area can be obtained by measuring from a cross section corresponding to each insertion amount of the press-fit terminal.

  Using the data of the insertion force Fi, the contact load Pi, and the contact angle θ shown in FIGS. 3 to 5, the normal drag N was obtained from the above equations (3) and (4). Further, the pressure Pd applied to the through hole at each moment of the insertion amount is obtained by calculation from the data of the friction coefficient μ, the data of the contact area S, etc., and the graph of the relationship between the pressure Pd and the insertion amount is shown in FIG. . The coefficient of friction μ is specific to the material and can be measured by a known method depending on the material. In FIG. 7, the horizontal axis represents the amount of insertion (mm), and the vertical axis represents the pressure Pd (MPa). As shown in FIG. 7, the pressure Pd increases as the insertion amount increases, and then decreases after passing through the maximum value. The maximum value in this graph is the maximum value of Pd of the present invention.

  Results of creating high-load type press-fit terminals of various shapes (Experiment Nos. 1 to 4), obtaining the maximum value of Pd by the above method, and examining the occurrence of through-hole plating breakage Is shown in Table 1. When the maximum value of Pd is 500 MPa or less, it is clear that the plating is not broken.

  In the press-fit terminal 1, the factor that affects the maximum value of the pressure Pd is mainly the shape of the connecting portion 13. For example, in the case of the needle eye type press-fit terminal shown in FIGS. 2A and 2B, the length and shape of the slit portion 14 in the connection portion, the thickness, shape, and connection of the beam members 15 and 16 in the connection portion 13. The maximum value of the pressure Pd can be changed by changing the length of the portion 13, the inclination of the connecting portion 13, and the like. There are an infinite number of options for determining the shape of the press-fit terminal so that the maximum value of the pressure Pd is 500 MPa or less. However, no matter what shape is selected, if the maximum value of the pressure Pd applied to the through-hole by the formed press-fit terminal is 500 MPa or less, it is possible to reliably prevent plating failure. become. This is a great advantage in designing and evaluating press-fit terminals.

  Although the press-fit terminal of the above embodiment has been described by taking the needle eye type as an example, the cross-sectional shape of the connecting portion is not particularly limited to the needle eye type, and may be another shape. For example, a solid type in which the cross-sectional shape of the connecting portion is not deformed when inserted, or a press-fit terminal such as a C-type, M-type, N-type, or H-type formed so that the cross-sectional shape of the connecting portion is deformed at the time of insertion. If the maximum value of the pressure Pd applied to the plating of the through hole is 500 MPa or less, it is possible to prevent the plating from being cut.

  The press-fit terminal of the present invention can be used as a connection terminal for various control boards, but particularly when used for connection between wire boards in electrical wiring of an automobile or the like, severe conditions such as on-vehicle high temperature and high vibration Is optimal as a connection terminal having high reliability.

It is explanatory drawing which shows the force added when a press fit terminal is inserted in the through hole of a board | substrate. (A) is a front view which shows an example of a needle eye type press fit terminal, (b) is sectional drawing in the AA of FIG. 2 (a). It is a graph which shows the relationship between the insertion amount of a press fit terminal, and insertion force Fi. It is a graph which shows the relationship between the insertion amount of a press fit terminal, and the contact load Pi. It is a graph which shows the relationship between the insertion amount of a press fit terminal, and contact angle (theta). It is a graph which shows the relationship between the insertion amount of a press-fit terminal, and the contact area S. It is a graph which shows the relationship between the insertion amount of a press fit terminal, and the pressure Pd added to a through hole.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Press fit terminal 2 Board | substrate 3 Through hole 3a Perimeter of through hole 3b Inner wall of through hole 13 Connection part of press fit terminal

Claims (1)

When a press-fit terminal is inserted in a press-fit state without applying contact oil to a through-hole of a circuit board formed by laminating and pressing a sheet of glass fiber impregnated with an epoxy resin, when inserted into the through-hole. A press-fit terminal, wherein the maximum value of the pressure Pd applied to the through hole represented by the following formula (1) is 500 MPa or less.
Pd = Fd / S (1)
In the above equation (1), Fd is the total force applied from the press-fit terminal to the through hole, and is expressed by the following equation (2), and S is the contact area between the press-fit terminal and the through hole.

In the above equation (2), μ is the friction coefficient between the press-fit terminal and the through hole, Pi is the contact load, and θ is the contact angle between the press-fit terminal and the through hole.

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